For facilitating the user to print or scan a large number of papers, an office machine (e.g. a printer, a scanner or a multifunction peripheral) is usually equipped with an automatic document feeder. By means of the automatic document feeder, a stack of papers can be successively fed into the office machine without the need of using the man power. Consequently, the papers can be printed, scanned or processed at a fast speed and in a labor-saving manner.
However, if the paper is not exactly placed on the inlet tray of the automatic document feeder in the beginning, the paper is aslant fed into the internal portion of the office machine. Under this circumstance, the printing or scanning quality of the office machine is deteriorated, and the paper is readily jammed in the automatic document feeder. The jammed paper becomes hindrance from performing the subsequent tasks. For preventing the skewed paper from being fed into the office machine through the automatic document feeder and obviating erroneous operations of the office machine, an automatic document feeder with a function of correcting a skewed paper was disclosed. Please refer to FIG. 1, which schematically illustrates a conventional automatic document feeder.
As shown in FIG. 1, the conventional automatic document feeder 10 comprises a paper pick-up device 11 and a transfer roller assembly 12. The paper pick-up device 11 comprises a pick-up roller 111 and a separation roller 112. The pick-up roller 111 is used for transporting a paper S into the internal portion of the automatic document feeder 10. The separation roller 112 is located downstream of the pick-up roller 111 for providing a friction force to separate the paper S, thereby preventing a plurality of papers S from being simultaneously transmitted into the automatic document feeder 10.
Please refer to FIG. 1 again. The transfer roller assembly 12 is located downstream of the paper pick-up device 11. In addition, the transfer roller assembly 12 comprises a shaft 121 and a roller 122. The shaft 121 is connected to a power source (not shown). The roller 122 is sheathed around and connected with the shaft 121. Consequently, the roller 122 is synchronously rotated with the shaft 121. Whereas, in a case that the shaft 121 is in a static status, the roller 122 is also in the static status.
When the pick-up roller 111 of the paper pick-up device 11 is rotated and contacted with the paper S, the paper S is transmitted to the separation roller 112 to be separated. The subsequent actions of the conventional automatic document feeder 10 will be illustrated with reference to FIG. 2. FIG. 2 schematically illustrates the actions of the conventional automatic document feeder.
As shown in FIG. 2, when the paper S transmitted through the separation roller 112 is moved to the transfer roller assembly 12, the shaft 121 and the roller 122 of the transfer roller assembly 12 are in the static status in order to hinder the paper S from being continuously advanced. Meanwhile, the paper S is continuously transmitted into the automatic document feeder 10 by the paper pick-up device 11, which is located upstream of the transfer roller assembly 12. Consequently, the front edge of the paper S is moved to the static roller 122 and slightly upturned. After the front edge of the paper S is completely moved to the roller 122, the function of correcting the skewed paper S is achieved.
After a preset time period, the front edge of the paper S is completely moved to the roller 122, and the function of correcting the skewed paper S is achieved. Then, the shaft 121 of the transfer roller assembly 12 acquires the electric power again to drive rotation of the roller 122. Consequently, the paper S is allowed to be transmitted through the transfer roller assembly 12.
Although the conventional automatic document feeder 10 is effective to correct the skewed paper S, there are still some drawbacks. For example, for correcting the skewed paper S by the conventional automatic document feeder 10, the rotation of the shaft 121 is an important factor for determining whether the paper S is continuously advanced or not. As previously described, the paper S is hindered by the static shaft 121 until the front edge of the paper S is completely moved to the roller 122. Once the front edge of the paper S is completely moved to the roller 122, the shaft 121 starts to rotate again. However, it takes a time period to accelerate the shaft 121 from the static state to a normal speed. Since each of the papers S to be transmitted needs the accelerating process, if a large number of papers are frequently processed by the conventional automatic document feeder 10, the paper-feeding efficiency is impaired and the processing time is largely prolonged.